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fxus61 kaly 272335 
afdaly

Area forecast discussion
National Weather Service Albany New York
635 PM EST Mon Feb 27 2017

Synopsis...
high pressure will build offshore tonight. The next chance of
rain and snow showers will be late tonight into Tuesday with a
warm front and low pressure moving into the Midwest. Showers will
increase in coverage through Tuesday night and there is a chance
of thunderstorms with a strong cold front Wednesday.

&&

Near term /until 6 am Tuesday morning/...
as of 630 PM EST...a cold front was oriented across the Saint
Lawrence valley with areas of high pressure behind the front and
off the Atlantic Seaboard. Temperatures across the region were
still mild for this time of year with readings in the upper 30s
to upper 40s.

Weak upper energy in the Ohio/Tennessee Valley and mid Atlantic tracking
east and the northern edge of the deeper clouds look to be
aimed for central and eastern New York and eventually into New England
through the night. How far north the edge of the clouds and
clearing set up will determine what areas can see temperatures
drop rapidly through the night. Areas that see the clouds will
see less of a drop in temperatures. There could be a sprinkle in
southern areas by daybreak as warm advection and isentropic
lift strengthens.

So, based on trends in satellite data and forecast guidance,
suspect kgfl could see less clouds and colder temperatures
tonight, maybe kddh but questionable. Going on the warmer side
of guidance in all areas except colder at kgfl. Lows in the 30s
but upper 20s northern areas.

&&

Short term /6 am Tuesday morning through Thursday/...
strong southwest boundary layer flow and intervals of clouds and
sun are expected Tuesday. Some uncertainty with timing of exit
of clouds and some scattered showers Tuesday morning. Still,
with the boundary layer warm sector shifting over our region and
the downslope southwest boundary layer flow, there should be at
least some periods of thinning of clouds or some sun in the
afternoon. Highs Tuesday in the mid 50s to near 60 but mid 40s
to around 50 northern areas.

Increasing uncertainty as to the timing and evolution of strong
upper energy approaching Tuesday night and Wednesday. There are
mixed signals in guidance as to the extent of moisture and
forcing that may or may not support enhanced coverage of showers
Tuesday night and thunderstorms Wednesday.

Different sets of guidance show small pieces of upper energy
ahead of the main upper impulse Tuesday night into Wednesday
morning with different timing and areal extent. There are
discontinuous and disjointed little centers of clouds and
precipitation, implying considerable coverage of clouds and
precipitation.

However, the warm sector should be centered over our region, so
thermal gradient forcing will be limited at best until the
approach of the cold front late Wednesday afternoon and evening.
Isentropic lift will be limited and strong southwest boundary
layer flow suggests downslope flow and areas of subsidence,
suggesting more scattered coverage of showers and thunderstorms.
The scattered coverage and some downslope also suggests some
potential intervals of thinning clouds and maybe some peeks of
sun Wednesday.

Boundary layer temperatures and decent mixing supports high
temperatures greatly exceeding records but if cloud and rain
coverage is greater on Wednesday, then temperatures may not
be as warm but still make the 60s in many areas. The warmth
will contribute to some marginal instability and including
scattered thunderstorms for the forecast Wednesday.

As far as severe potential, the upper system is less amplified
than the event last weekend and is positively tilted. The
thermal gradient along the cold front is not quite as extreme
but still strong. Midlevel lapse rates are not as steep as the
event last weekend. Upper jet structure is not supportive of
upper divergence like it was in the event last weekend. Still,
the instability and the strength of the low level jet energy
along with the low level forcing could still support some
enhanced thunderstorm activity but the signals are not as strong
as last weekend.

Keeping thunderstorms in the forecast Wednesday afternoon and
Wednesday evening but not including enhance wording yet. If
guidance tonight and tomorrow show a clearer severe weather
signal it will be added then. Highs Wednesday in the 60s but
near 70 in central and southern areas if we get some periods of
thinning of clouds.

The front tracks through Wednesday evening and night and then
strengthening cold advection Thursday. Highs Thursday around 40
to mid 40s but some upper 20s to mid 30s northern areas where
some lake effect snow shower activity could occur.

&&

Long term /Thursday night through Monday/...
on Friday, medium-range deterministic models and ensembles indicate
that a quick-moving shortwave will move through the longwave eastern
Continental U.S. Trough, but guidance differs on the track and strength of the
surface reflection. Most guidance aside from the GFS takes the
surface low/trough well to our south, keeping most of our area dry
aside from perhaps some lake-effect snow showers over the western
Adirondacks. The last several runs of the GFS have been consistent
in a stronger, further north low that would give much of our area a
quick shot of accumulating snowfall. Will lean toward blended
solution of 30 pops in the south/20 pops in the north for now. High
pressure then builds in for Friday night into Saturday, leading to
dry but cool conditions as 850 mb temps may be near -15 to -20c. A
quick airmass modification is likely for Sunday, as the upper trough
shifts east of the region and height rises/warm air advection ensue. A few showers
may be possible with the warm advection Sunday.

&&

Aviation /00z Tuesday through Saturday/...
skies were variable this evening with some breaks in the clouds
noted over kalb and kpsf while kgfl and kpou had a broken to
overcast mid deck. Expect the cloud bases to gradually lower
through the taf period, but still remain VFR. A few light rain
or snow showers are possible after 08z as a warm front lifts
into the region, but confidence is not high enough for an
explicit mention attm. Will continue with vcsh 08-15z.

Winds have already diminished generally from the the southwest
at 5 to 10 kts. Winds will become nearly calm or light and
variable late tonight before going south-southeast at around 5
kt late Tuesday morning.

Outlook...

Tuesday night: moderate operational impact. Chance of rain showers.
Wednesday: moderate operational impact. Windy with gusts to 30.0 likely rain showers...tsra.
Wednesday night: moderate operational impact. Likely rain showers...tsra.
Thursday: low operational impact. Breezy no sig weather.
Thursday night: no operational impact. No sig weather.
Friday: low operational impact. Slight chance of shsn.
Friday night: no operational impact. No sig weather.
Saturday: low operational impact. Breezy no sig weather.

&&

Hydrology...
drier and much colder air over our region through
tonight with a few light showers possible around daybreak
Tuesday. Then, mainly dry weather continues through Tuesday but
temperatures are expected to warm through Wednesday and snow
melt should occur into the middle of next week. The next chance
of widespread rainfall will be Tuesday night through Wednesday.

The latest mmefs shows minor rises in area rivers and streams
with the system Tuesday/Wednesday.

For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the advanced hydrologic prediction service /ahps/ graphs
on our website.

&&

Aly watches/warnings/advisories...
CT...none.
New York...none.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...NAS
near term...11/NAS

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